CMOS planar 2D micro-fluxgate sensor

An electronic compass made of a new planar 2D micro-fluxgate sensor is presented. The magnetometer is integrated in a standard CMOS process, and uses a post-processed cross shape ferromagnetic amorphous core. This core is diagonally placed above a single square excitation coil common to both measurement axes. The silicon chip includes the driving and readout electronics, the excitation and pick-up coils made of the two CMOS process metallization layers. The ferromagnetic core is integrated from commercially available amorphous metal ribbons, by using a post-process compatible with standard IC technologies. Such a ferromagnetic core presents outstanding magnetic characteristics compared to usual electroplated cores. The micro-fluxgate works with a pulse shape driving current which allows the sensor output to be independent of the driving frequency. The current pulse width ratio of 1:8 reduces drastically the power consumption. For magnetic fields within ±60 μT, the micro-fluxgate sensor exhibits a magnetic sensitivity of 3760 V/T at 125 kHz with an amplification gain of 26.4 dB. The angle error on the Earth’s magnetic field is ±1.5°. The chip has a power consumption of 12.5 mW for a 20 mApeak driving current; its area is 5.3 mm2.